Consider the half-reaction Cr³⁺(aq)→ Cr₂O₇²⁻(aq). When the equation is balanced in acid solution, the coefficient for water will be ________, and the number of electrons transferred will be ________.

Question

Quizplus · Accepted Answer

First, we need to balance the equation by adding H+ ions and H2O molecules. The balanced equation in acid solution is: Cr^{3 + 14H+ + 8}(aq) → Cr₂O₇^{2− + 3H2O + 8}(aq) Next, we need to identify the species that undergoes a change in oxidation state. Here, we see that chromium (Cr) changes from +3 to +2, so it gains one electron. Each sulfur (S) atom in thiosulfate (S2O32-) changes from +2 to +4, so it loses two electrons. Therefore, in total, there are 8 electrons transferred (4 from each S2O32- ion). So the answer is (C) 7 water molecules and 6 electrons transferred. Note that the coefficient for water is one less than the total number of H+ ions added, which is 8 in this case.

Consider the Half-Reaction Cr3+(aq)→ Cr2O72−(aq)

Consider the Half-Reaction Cr³⁺(aq)→ Cr₂O₇²⁻(aq)